I see no evidential reason to believe it. If you’re going to claim accident, you need evidence which establishes probability. One-off doesn’t cut it.
Also you shouldn’t assume that no one else has ever written or drawn anything.
To me it looks like a scribbled circle with a “dot” as an accidental (or illusory) artifact.
If you want a good image, why not ask Creighton for his digital one?
Post Edited (27-May-14 23:11)